People doing cell cultures often end up having more cells than needed or might not need the cells at that point of time. In such cases, the cells can be stored by freezing for later use. The process of preserving the cells by freezing is known as cryopreservation. The freezing stocks can be stored in liquid Nitrogen for an indefinite period.
Freezing can however, cause damage to cells by the formation of ice crystals, pH change. To avoid this, a cryopreservative agent such as DMSO (Dimethyl sulfoxide) was added to cells before freezing. DMSO lowers the freezing point and prevent ice crystal formation inside the cells.
The freezing process is carried in 2 steps
- The cells were cooled slowly from room temperature to -80 degrees C either in a freezing chamber or Mr Frosty in -80 degrees C freezer . Mr.Frosty is just a container filled with isopropanol. The advantage of Mr.Frosty is controlling the rate of cooling that helps freezing the cells successfully. The cooling rate in this container will be repeatable -1 degrees C/min.
- After leaving at -80 degrees C for a day, the vials with frozen cells are transferred to liquid nitrogen (-196 degree C).
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